In recent years, in an image reading apparatus, such as a personal facsimile, small light emitting diodes (hereinafter referred to as an LEDs) with a low power are starting to be used as a light source of a reading light source apparatus, due to improvements in an output of such LEDs and a raise in the sensitivity of a CCD type sensor as a light receiving element. In a conventional linear light source apparatus equipped with such LEDs as light sources, the number of the light sources is reduced and a light guiding member in which light emitted from the light source enters the light guiding member and the light is led towards a desired direction, is used so as to obtain uniform lighting intensity.
Japanese Laid Open Patent No. 2001-159796 discloses a light guiding member in which a light direction changing face having an inverted V character shape in a cross sectional view thereof taken along a short side direction thereof is formed at a position facing the light emitting face. Since the light emitting face having the curvature which is smaller than those of other portions is formed, the light which is emitted from the light emitting face is condensed, and, for example, the light having directivity is irradiated to a document face.
Moreover, Japanese Laid Open Patent No. 2000-59571 discloses a light guiding member whose light emitting face has a lens face shape which consists of a shape of such as a circular arc or an arc of an ellipse, in a cross sectional view thereof taken along a short side direction of the light guiding member, in which two light direction changing faces are provided at positions where they face the light emitting face.
Moreover, Japanese Laid Open Patent No. 2005-229647 discloses a light source apparatus having two light emitting units facing each other, in each of which a light source is disposed on an end face of each light guiding member. The light guiding member is made of resin having high optical permeability, such as acrylics and polycarbonate, or optical glass having high optical permeability, and a light emitting face is formed on one side surface. For example, one or more face mounting type LED is attached to the light source. While the light which enters the one end face of a light guiding member from the LED, is reflected inside the light guiding member, the light is guided in a longitudinal direction, so as to emit the light in a direction of an arrow from the light emitting face. Each lighting unit is arranged so that light emitted from each light emitting face may be irradiated onto a document reading face in a document face, that is, each of them irradiates the same document reading face area.
However, since the light guiding member disclosed in Japanese Laid Open Patent No. 2001-159796 or 2000-59571, irradiates light to the document reading face from one direction, if there are creases or uneven portions formed by pasting, on a paper face which is a work piece to be irradiated, a shadow is produced. Moreover, since in the light source apparatus disclosed in Japanese Laid Open Patent No. 2005-229647, light is irradiated to a document reading face from two directions, a shadow is not produced even if there are creases or uneven portions formed by pasting. However, since it is necessary to arrange two light guiding members, the entire apparatus becomes large and demand of a miniaturization cannot be achieved.
In view of the above mentioned problem, described below is a light guiding member and a bifurcated linear light source apparatus capable of irradiating light to a document reading face from two directions and realizing the miniaturization of apparatus.
According to one aspect of embodiments, the present light guiding member has a light direction changing face which extends in a longitudinal direction of the light guiding member and a light emitting face which faces the light guiding member, wherein the light direction changing face includes two faces arranged so that vertical planes which extend in the longitudinal direction and are respectively vertical to the two faces, intersect with each other. Since the light direction changing face of the light guiding member is formed by two faces arranged so that vertical planes which are vertical to the respective two faces extending in a longitudinal direction may intersect with each other, whereby light can be emitted in two directions from one light guiding member. When the light guiding member is applied to a light source apparatus, irradiation of the light to a document reading face from two directions is easily configured.
According to another aspect of embodiments, a relation of θ1≧θ2 may be satisfied, when an intersection angle formed by the vertical planes at an intersection thereof is represented as θ1, and an angle which is formed by center-of-curvature lines which pass through respective two intersection points of the vertical faces and the light emitting face, is represented as θ2. The “center-of-curvature line” means a line which passes through the center point of a circle or a curved surface of a light emitting face. In the case, since the angle of each light which is emitted from the light emitting face becomes large, areas where the light direction changing face and the light emitting face are formed, can be narrowed, so that the flexibility of the design is improved when a shape design is performed, and a formation of the projection section for reinforcing the light guiding member becomes easy, and further, fixation of the light guiding member to the light source apparatus becomes easy.
According to still another aspect of embodiments, in the light guiding member, the light direction changing face may be in a concave shape, with respect to a short side direction of the light guiding member. When each light direction changing face of the light guiding member is formed in the shape of a concave with respect to the direction of a short side of the light guiding member, the light whose direction is changed by the light direction changing face is converged so as to be incident on the light emitting face, so that it is possible to respectively converge and emit light which is emitted in the two directions from the light emitting face, regardless of the shape of the light emitting face.
According to a further aspect of embodiments, the present light guiding member may be in a rod shape, which has a light direction changing face which extends in a longitudinal direction of the light guiding member and a light emitting face which faces the light guiding member, wherein the light emitting face of the light guiding member is formed of two curved surfaces in which respective curvatures thereof are equal to or different from each other. Thus, since the light emitting face of the light guiding member is formed of two curved surfaces in which the curvatures thereof are equal to or different from each other, it becomes easy to converge and emit light, which is emitted in the two directions from the light emitting face, in arbitrary directions respectively.
According to a still further aspect of embodiments, a bifurcated linear light source apparatus comprises a LED, a light guiding member which is made up of a transparent rod shape member, and which emits light generated by the LED, in two directions, from a longitudinal direction side face of the transparent rod shape member, and a reflection mirror which reflects the light emitted in one of the two directions, to the other direction of the two directions. Thus, the structure for irradiating the light from two directions to a document reading face becomes simple. Moreover, since only one light guiding member is used, the miniaturization of apparatus can be realized.
According to a still further aspect of embodiments, a bifurcated linear light source apparatus may comprise the above light guiding member, a light source provided so as to face an optical incidence section which is provided at least in one of both ends of the light guiding member in the longitudinal direction, and a reflection mirror which reflects light emitted from the light emitting face in one of the two directions, to the other direction of the two directions, in which a length of the reflection mirror is the same as that of the light emitting face of the light guiding member, and the reflection mirror is provided in a position approximately symmetrical to the light emitting face with respect to a face vertical to a center of a document reading face. Thereby, the structure for irradiating the light from the two directions to the document reading face becomes simple, and moreover, since only one light guiding member is used, the miniaturization of apparatus can be realized.